BTTF theories that the game has (sorta) vindicated...

If you consider the Game canon, at least partially (by virtue of Bob Gale's involvement), then you must admit it has vindicated, or at least tried to, several theories regarding how time travel works in BTTF...here goes...

[B]1. The timeline transforms around time traveller's, if they are outside their own time, and if another time traveller goes further behind them into the past and changes it

Now, this is probably the least argued theory, and has pretty much already been confirmed as the official explanation by Bob Gale in the official FAQ, but still, there are people who wonder about stuff like how Old Biff made it back to LP 2015 rather than 2015-A, and why weren't Marty, Doc and Jennifer stranded in LP 2015 without a time machine...the timeline transforming around time traveller's is pretty much a given, considering that there are no parallel universes in BTTF...Old Biff definetly returned to 2015-A (the only version of 2015 in existence), and Marty, Doc and Jennifer were just shunted onto the new timeline by virtue of being protected from the ripple effect, simply cuz there was no where else for them to go...

But, the sight of 1931 Hill Valley disappearing before Marty and Doc's eyes because of Edna's trip back in time...should convince everyone of this theory...

2. Even if a time traveller's existence is erased, his/her existence during the span of a time travel trip to the past, and his/her actions (and their impact) will not be forgotten/undone...or in other words, even if time traveller's come from futures which are later erased, their brief existence in the past stays intact (i.e. the so-called 'echo theory')

This is the one which kinda solves the major paradox of Old Biff preventing the existence of the time machine, or even himself at that age, by changing the past. Even in the new 'A' timeline, although Lone Pine Old Biff could never exist (and neither could the time machine), he would still appear from a now non-existant 2015, give the Almanac to his younger self, and then return to the future of this new timeline...even though he is erased from existence when he arrives in 2015-A...his brief existence in 1955 will not be retroactively erased...which is why Marty is able to see him in '55 later.

In the game, we have no less than three versions of Doc running around 1931 (and I'm talking about Doc from 1986, not teenage Emmett Brown)...they are LP Doc (the Doc from the movies, and from Episodes 1 and 2), FCB Doc (from the Citizen Brown reality) and the new version of Doc that I'll call 'NEW Doc' for simplicity

LP Doc travels back to 1931, assumes the persona of 'Carl Sagan' and is accused of being the speakeasy arsonist and arrested, before Marty rescues him...he is erased from existence as soon as he departs from 1931. He is replaced by a new version-FCB Doc...and yet, although LP Doc's timeline has been erased, his previous existence and actions in 1931 are not undone nor is he forgotten...people still remember 'Carl Sagan', which is indeed the identity FCB too adopts, and people naturally mistake him for LP Doc...in fact, if FCB Doc travelled to, say August 25th 1931, then he would be able to see LP Doc...we would have two Docs from different realities co-existing, though one would be from a non-existent timeline...and later, when FCB Doc is erased, we have NEW Doc show up in 1931...and yet again, FCB Doc, though he faded from existence, is not forgotten by Marty or anyone else in 1931...

3. Time travellers do not instantly gain new memories if their past selves gain them during a trip.

This one's for people who wonder if, when BTTF1 Marty saw Biff's goons on the stage (something which didn't happen in the original timeline as seen in the first film), did BTTF2 Marty, who knocked out the goons, suddenly remember seeing them? Or, if '85 Doc suddenly gained memories of the conversation he had with '55 Doc, while the conversation was going on? Or why '85 Doc didn't remember finding his tombstone in 1955 or dressing Marty in that outfit?

The answer is no.

Time traveller's do not suddenly gain new memories, if their past selves lives diverge due to their actions (or someone else's) from what they themselves remember. This is clearly illustrated in the game, where Doc tells Marty how he doesn't remember performing experiments out in the open, even as they watch the young Emmett Brown performing experiments in the open (owing to the influence Marty's trip to 1931 has had on his life).

However, time traveller's might gain these new memories once they return to their own time. Doc, when he shows up from 1986 in Episode 5, remembers Marty in 1931 and all the events of 1931 as they happened in the new timeline...then again, that's likely because he's a completely different version altogether. What is clear, is that time traveller's don't instantly gain new memories...

4. Doubles can exist...if the timeline has been drastically altered.

People have long wondered whether or not there were alternate versions of Marty and Doc in Switzerland and at the asylum, while the regular LP versions were in 1985-A, since their counterparts in this timeline couldn't have time travelled. Well, the game shows that doubles can exist. There apparently IS another Marty in the FCB timeline, who is still around, though Marty never runs into him...then again, we don't see him so we can't be 100% certain but its strongly implied.

That of course, does bring about the question of why 'our' Doc had to fade away to be replaced by FCB Doc...if doubles can exist...or why Marty didn't fade to be replaced by FCB Marty?

@63cohen said: Small problem, I think the CB Marty was replaced with the regular Marty once he came into the timeline. His parents regarded him as Marty, and over the course of that day, either the CB Marty was watching Frankenstein a few times over, or he didn't exist.

His parents say he went to a Maths camp and so wouldn't be there anyway.

This is good. The only thing I have a problem with is the doubles one. Do you mean doubles do exist if the timeline is altered in such a way so they never go back in time in the first place?

Also number 2 is essentially a way of forcing the parallel theory and the singular universe theory together to support the way BTTF works. I'm not saying it's bad, I've been trying to think of a way to do this for ages.

@Marty Mcfly III said: His parents say he went to a Maths camp and so wouldn't be there anyway.

This is good. The only thing I have a problem with is the doubles one. Do you mean doubles do exist if the timeline is altered in such a way so they never go back in time in the first place?

Exactly.

I feel a logical explanation for this phenomenon would be something like this-if the time traveller has altered the timeline such that his (slightly) younger self doesn't time travel, then it's obvious that the younger self ceases (in terms of strict causality) to be the younger self of the time traveller and becomes an alternate self instead.

Take Marty, in the films (the Game does confuse this issue somewhat). When TP Marty returns to 1985 10 minutes early in BTTF1, he sees LP Marty being chased by the Libyans and basically going through the same sequence of events he went through. Now LP Marty has grown up in a timeline different from TP Marty, with a different version of the McFly family...and yet, because he goes through the same events that lead to his travelling back in time at the exact same moment as TP Marty, he is, for all intents and purposes TP Marty's past self...leading to a loop where Marty goes back in time, returns 10 minutes early, and watches himself go back in time in the first place. TP Marty=LP Marty, in terms of causality, as a result of this (there is the whole memory issue of course, but there are explanations for that). Whereas, in 1985-A, Marty-A DOES NOT travel back in time on October 26th 1985, and thus, he logically CANNOT become the Marty we see on screen returning from a trip to the future.

@Marty Mcfly III said: Also number 2 is essentially a way of forcing the parallel theory and the singular universe theory together to support the way BTTF works. I'm not saying it's bad, I've been trying to think of a way to do this for ages.

Yeah, that's pretty much the way it is. BTTF operates on the single timeline theory, but has incorporated aspects of the multiple timelines theory in order for it to work...pretty much every timeline, in some form or another, owes its very existence, to an event, person or object originating from a previous timeline.

I feel a logical explanation for this phenomenon would be something like this-if the time traveller has altered the timeline such that his (slightly) younger self doesn't time travel, then it's obvious that the younger self ceases (in terms of strict causality) to be the younger self of the time traveller and becomes an alternate self instead.

Take Marty, in the films (the Game does confuse this issue somewhat). When TP Marty returns to 1985 10 minutes early in BTTF1, he sees LP Marty being chased by the Libyans and basically going through the same sequence of events he went through. Now LP Marty has grown up in a timeline different from TP Marty, with a different version of the McFly family...and yet, because he goes through the same events that lead to his travelling back in time at the exact same moment as TP Marty, he is, for all intents and purposes TP Marty's past self...leading to a loop where Marty goes back in time, returns 10 minutes early, and watches himself go back in time in the first place. TP Marty=LP Marty, in terms of causality, as a result of this (there is the whole memory issue of course, but there are explanations for that). Whereas, in 1985-A, Marty-A DOES NOT travel back in time on October 26th 1985, and thus, he logically CANNOT become the Marty we see on screen returning from a trip to the future.

The problem with this theory is that it kinda breaks down when someone goes back in time to fix something, therefore preventing their past self from travelling back in time to prevent it. It's in the game, like you said, when Marty and Doc go back to 1876. Once they've fixed everything and come back to the future there should be duplicates of them because the duplicates never went back in time to fix things.

@Marty Mcfly III said: The problem with this theory is that it kinda breaks down when someone goes back in time to fix something, therefore preventing their past self from travelling back in time to prevent it. It's in the game, like you said, when Marty and Doc go back to 1876. Once they've fixed everything and come back to the future there should be duplicates of them because the duplicates never went back in time to fix things.

An acceptable paradox then? Theoretically there should be a time ripple effect in this case. In BTTF 3, Marty never would have seen the tombstone, so he never would have gone back to save Doc. Marty should have faded out after a while.

@Marty Mcfly III said: The problem with this theory is that it kinda breaks down when someone goes back in time to fix something, therefore preventing their past self from travelling back in time to prevent it. It's in the game, like you said, when Marty and Doc go back to 1876. Once they've fixed everything and come back to the future there should be duplicates of them because the duplicates never went back in time to fix things.

@Marty Mcfly III said: An acceptable paradox then? Theoretically there should be a time ripple effect in this case. In BTTF 3, Marty never would have seen the tombstone, so he never would have gone back to save Doc. Marty should have faded out after a while.

Yeah, I agree...these to my mind are some of the biggest paradoxes in BTTF. And while one might be able to find a way round the tombstone problem, with the Game, it just stretches the suspension of disbelief...

Nearly every time travel trip to the past in the game arguable causes (or should cause) a paradox of some sort.

Trip 1: Marty goes back to the past to save Doc in 1931 because he reads the newspaper article about Doc getting shot dead by Kid Tannen's goons. But when he rescues Doc, then the newspaper he saw in Edna's house in 1986 wouldn't have the story about Doc and thus Marty wouldn't know of Doc's situation and wouldn't have been able to travel back and rescue him from it.

Trip 2: Marty goes back in time 6 hours because he starts fading and reads the next days newspaper (which has now been changed by the ripple effect owing to Trip 1) which states that Arthur McFly was killed by Kid Tannen's goons. But Marty is able to save Arthur McFly which again causes a paradox...since now that Arthur has been saved, Marty should never have started fading away in the first place and would never had read the newspaper about Arthur's death, and thus wouldn't have a reason to travel back 6 hours. And yet, Marty does see his 6 hour younger trip going back in time in the Delorean, on a mission he has no reason to undertake.

Trip 3: Marty and Doc return to 1931 again to ensure that Kid Tannen is arrested, because when they returned to 1986, they realised that their previous actions had altered history and the Tannen Mob had therefore taken over Hill Valley...but once they ensure Kid Tannen's arrest and restore the normal timeline, then they would have logically had no reason to go back to 1931 (when they last returned to 1986) in the first place, as there would have been nothing wrong with '86. (Then again, alternate timelines are special cases, and this is similar to the 1985-A situation in the film...so I suppose the paradox may be easily ignored).

Trip 4: The existence of the FCB timeline is itself based on a paradox, as in this reality, Doc didn't even come up with the IDEA of the time machine (which at least, he HAD come up with in 1985-A). However, the real paradox is that Marty and Doc have no motivation to go back to 1931 and prevent the existence of the FCB timeline, if the FCB timeline was 'already' erased at the time they initially 'returned' to 1986 after Trip 3. However, as mentioned above, alternate timelines, like 1985-A, do seem to be special cases, so again the paradox could somehow be ignored. Then again, Marty's actions in 1931 lead to a new timeline where Doc continued to live in 1986 after BTTF3; therefore there was no estate sale which Marty was attending, and in this timeline, since Doc wasn't missing, Marty wouldn't have any reason to go back in time in the first place...so the entire sequence of events leading to this timeline would be undone logically...

Trip 5: Edna goes back in time and destroys Hill Valley in 1876...the obvious paradox being that she has presumably negated the existence of pretty much EVERY resident of Hill Valley after 1876...including Doc and Marty (without whom her trip to the past would be impossible) and herself! Again, I suppose the alternate timeline special case applies (though it would be really hard to figure that out in this case).

Trip 6: Marty and Doc go back to 1876 in order to prevent Edna from destroying Hill Valley only on the basis of their encounter with the aged Edna in the destroyed Hill Valley timeline. Once they erase that timeline and that version of Edna, they would have no reason to go back in the first place. Same issue as Marty and Doc losing their motivation to erase 1985-A, the Tannen Mob and FCB timelines once they erase them.

True these should all be paradoxes but what ever happened to your idea about the original versions of the people coming from the meta-universe ( i can't remember if we talked about this in this thread or another one). I thought this idea was supposed to prevent these paradoxes from occurring.

I think its pretty sure that two versions of the same person cant co-exist when they are both at their native time. We have never seen this have we?

The question is why does normaly the returning time-traveler get priority over the other one (ie, the copy of them that never time traveled due to the thing that needs to be fixed already being done gets erased). However, in the CB future it was the time-traveling doc that was erased instead.

---Incidently, In ¨real¨ time travel theories, it makes sense that you could never do anything deliberate in the past - because any change you make would already be changed and youd never go back.This ties in with this principle;http://en.wikipedia.org/wiki/Novikov_self-consistency_principleWhich personaly makes a lot of sense to me. Doesnt stop accidently changes or observation trips, mind :P

@Marty Mcfly III said: True these should all be paradoxes but what ever happened to your idea about the original versions of the people coming from the meta-universe ( i can't remember if we talked about this in this thread or another one). I thought this idea was supposed to prevent these paradoxes from occurring.

True, and I've always believed that. I'm just saying that logically, in terms of conventional thinking, all of these WOULD be paradoxes. Also, my theory about this meta-dimension (or rather, time traveller's from erased timelines) is pretty much just a way to rationalise how BTTF operates. The truth is, that most theories about BTTF time travel are fan speculation and the writers never really gave the paradoxes much thought. So in BTTF1, we saw Marty preventing his own birth, causing a paradox, and therefore he starts to fade from existence...the issue of why Marty would even have briefly existed to prevent his birth had he prevented it is an issue the filmmakers didn't really delve into, and hence the 'echo theory' was thought up to explain it. With BTTF2, you pretty much have to come up with all sorts of convoluted theories to explain away the paradoxes.

Truth is, that Bob Gale and Bob Zemeckis have us very little in the way of time travel theory in the movies, or in interviews and commentaries, and very little explanation of paradoxes in the movies. Bob Gale kinda addressed the issue of Marty and Jennifer's future selves still existing despite their past selves having jumped into the future by suggesting that maybe the logical 'extrapolation' of the time Marty and Jen left 1985 took into account their eventual return (and then he admits this doesn't make sense). He even admits that the gradually fading photograph doesn't make sense, and was in there for symbolism. He does confirm the thing about the timeline transforming around time travellers, if another time traveller changes the past. And then there's the chalkboard drawn by Doc in BTTF2 to explain the alternate 1985...Bob Gale admits on the DVD commentary (which I read a transcript of somewhere) that what they were explaining here WAS the parallel timelines theory...although he has stated elsewhere that there are no parallel timelines in BTTF.